<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<style type="text/css">
			*{
				margin: 0;
				padding: 0;
			}
			.first>li{
				display: inline-block;
				position: relative;
			}
			li{
				width: 100px;
				list-style-type: none;
			}
			ul ul{
				display: none;
				position: absolute;
			}
			.first>li:hover>ul{
				display: block;
			}
			.first>li:hover{
				background-color: red;
			}
		</style>
	</head>
	<body>
		<div style="text-align: center;">
			<ul class="first">
				<li>一级菜单
				<ul>
					<li>二级菜单</li>
					<li>二级菜单</li>
					<li>二级菜单</li>
					<li>二级菜单</li>
				</ul>
				</li>
				<li>一级菜单
				<ul>
					<li>二级菜单</li>
					<li>二级菜单</li>
					<li>二级菜单</li>
					<li>二级菜单</li>
				</ul>
				</li>
				<li>一级菜单
				<ul>
					<li>二级菜单</li>
					<li>二级菜单</li>
					<li>二级菜单</li>
					<li>二级菜单</li>
				</ul>
				</li>
			</ul>
		</div>
	</body>
</html>
